1. Field
This disclosure relates generally to reception of digitally modulated wireless signals, and more specifically to reception of wireless signals modulated with both spread spectrum and non-spread spectrum modulation.
2. Related Art
Direct sequence spread spectrum communications systems operate by encoding each data bit over a number of modulated channel symbols, which are referred to as chips. Each channel symbol also encodes a pseudorandom data sequence. Although a direct sequence spread spectrum communications system includes modulation and receiving equipment that process the signal at the modulated chip rate, the user data throughput is reduced by the spread spectrum encoding. Direct sequence spread spectrum receivers correlate a received signal with a reproduction of the pseudorandom data sequence to extract the encoded data. The operation of direct sequence spread spectrum systems allows the communication of data with enhanced interference rejection.
One direct sequence spread spectrum communications application is the IEEE 802.15.4 communications standard. The incorporation of direct sequence spread spectrum signals in the IEEE 802.15.4 communications standard allow reliable communications over an extended range. This use of direct sequence spread spectrum signals, however, reduces the data throughput of IEEE 802.15.4 systems relative to the total bandwidth consumed by the system and the corresponding capacity of the processing hardware of the communications equipment.
Therefore, a technique that would allow the hardware used to implement an IEEE 802.15.4 receiver to communicate at a higher data rate throughput than is supported by that standard expands the usability of that hardware.